1. Field of the Invention
This invention relates to an electrophotographic photosensitive member provided with a photosensitive layer containing specific hydrazone compounds, and more particularly, it relates to an electrophotographic photosensitive member having enhanced sensitivity and improved durability to repeated operations.
2. Description of the Prior Art
Selenium, cadmium sulfide, zinc oxide, etc. have hitherto been known as photoconductive materials used for electrophotographic photosensitive members. In contrast their many advantages, for instance, chargeability to suitable potentials in a dark place, slight dissipation of charge in a dark place, and fast dissipation of charge being possible by light irradiation, these photosensitive materials are lack of film forming property in themselves, with a few exceptions such as the case of amorphous selenium, and have the disadvantage of poor retention of the charge given to their surface.
On the other hand, besides these inorganic photoconductive materials there are known organic ones including, for example, high-molecular photoconductive materials such as poly(N-vinylcarbazole), N-acrylamidemethylcarbazole polymer disclosed in Japan Pat. Appl. Laid-open No. 85337 (1975), and 6-vinylindole(2,3-6)quinoxaline polymer disclosed in Japan Pat. Appl. Laid-open No. 93432 (1975); and low-molecular photoconductive materials such as 2-aza-9-fluoroenones (Japan Pat. Appl. Laid-Open No. 71236/1973), triarylpyrazolines (U.S. Pat. No. 3,824,099), bis(p-dialkylaminostyryl)phenyl (Japan Pat. Appl. Laid-open No. 31773/1975), 2, 6-bisstyrylpryidines (Japan Pat. Appl. Laid-open No. 94828/1976), spiro-pyrazolines (Japan Pat. Appl. Laid-open No. 112637/1979), N-(p-dialkylaminophenyl)carbazoles (Japan Pat. App. Laid-open No. 119925/1979), 2, 5-bis(p-dialkylaminophenyl)-1, 3, 4-oxadiazoles (Japan Pat. Appl. Laid-open No. 121742/1979), bis(p-dialkylaminophenyl)alkanes (Japan Pat. Appl. Laid-open No. 17105/1980), bis(p-dialkylaminophenyl)quinolylalkanes (Japan Pat. Appl. Laid-open No. 108667/1980), hydrazone compounds (U.S. Pat. No. 4,150,987), 9-styrylanthracene compounds (Japan Pat. Appl. Laid-open Nos. 94828/1976 and 94829/1976), and 4-chlorooxazole compounds (Japan Pat. Appl. Laid-open No. 53278/1980). However, these organic photoconductive materials are not of practical use because of their low sensitivity.
Such being the case, in recent years laminated members have offered which comprise two photosensitive layers provided with separate functions, that is, a charge generation layer and a charge transport layer which contains an organic photoconductive material. Electrophotographic photosensitive members comprising such photoconductive layers of laminate structure have been improved in certain points such as sensitivity to visible light, charge bearing capacity, and surface strength, in which photosensitive members employing organic photoconductive materials had been deficient. Such improved electrophotographic photosensitive members have been disclosed, for example, in U.S. Pat. No. 3,837,851 (Japan Pat. Appl. Laid-open No. 105537/1974), U.K. Pat. No. 1,453,024 (Japan Pat. Appl. Laid-open No. 90827/1976), and U.S. Pat. Nos. 3,484,237 and 3,871,882.
Electrophotographic photosensitive members employing existing organic photoconductive materials are however still unsatisfactory in sensitivity and disadvantageous in that notable variations of surface potential are caused by repeated charging and exposure, and in particular increase of potential in light area and decrease of potential in dark area are remarkable in that case.